Editing Atari 1200XL Troubleshooting Guide (section)

=== POKEY (U24, C012294) – Audio/Keyboard/SIO ===
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''POKEY Fault Symptoms'''
|-
! Symptom !! Probable Cause !! Verification
|-
| No sound from any channel || POKEY audio output failure || Check audio output at pin 37 (AUDIO). Verify +5V on pin 17 (Vcc).
|-
| Missing tones (some channels only) || Partial POKEY failure || Run Audio Visual self-test. Each channel plays sequentially (Voice 1–4).
|-
| Some keyboard keys fail || POKEY keyboard scan fault or keyboard membrane || Check POKEY scan outputs K0–K5 (pins 18–20, 23) and responses KR1–KR2 (pins 16, keyboard connector pins 1,3).
|-
| All keyboard keys fail || POKEY failure or keyboard cable disconnected || Verify keyboard Molex connector (J8) is seated. Test POKEY keyboard scan lines.
|-
| SIO communication failure (no disk/cassette access) || POKEY serial I/O fault || Check SOD (pin 28, serial output), SID (pin 24, serial input), ACLK (pin 27), BCLK (pin 26).
|}